H2 Physics Practical (2)

H2PhysicsPractical Preparation● Bringcurveruler Settingup● Experimentsinvolvingstring○ Tyingknots○ Step1isalwaystomaketoothinstringthicker,so2plyit.○ Ifuwantstringtobemovable,1knotwilldo○ Ifuwantstringtobeunmovable,donottieadeadknot.Method1:1knotbyhangingstringaroundtautstring,followedby1knotbytautstringaroundhangingstring.○ Alternatively,clovehitch:suitableforbothmovableandunmovablepurposes.2clockwiseloops. ● Retortstand○ Noteperspectiveasdrawnindiagram○ Seeifursupposedtohangstufffromthebossorfromtheclamp○ Bossisthesmallthingthatisattachedtotheretortstandneckdirectly○ Clampistheadditionalthingkiapedontotheboss,hasarodandhaspincers ● Circuits○ Multimetersusedasammetersaresetuptogetherwithcircuitcuzitispartofthecircuit

○ Multimetersusedasvoltmetersaresetupattheveryendcuzitisalonewolf○ Multimetersusedasresistor:startwithlowestresistancesetting.“1.”meanssettingistoolow.Turnitup. Measurements● Length○ Maynotalwaysbeverniercaliper.Istheobjectsmallenough?Ruler.○ Verniercaliper■ Zeroerror=0.00cm(2dp)● Repeatif:○ Recordingtime○ Usingverniercaliper/micrometerscrewgauge○ Largepossibleerror■ Egflimsyobject■ Egnonuni-dimensional,differentpartsofobjecthavedifferentdimensions○ 2marks● Noneedtorepeatif:○ 1mark○ Smallsmallpossibleerror■ Eglengthofsmt■ Electricalexperiments● Remembertowriteyourunits● Record=/=measure.Recordmeanstakethevaluethatqntellsyou. Apparatus● Multimeter○ Knowhowtoproblem-solvethisdevil○ Ifusedtomeasureresistance,itshouldbeconnectedtoresistorwithoutcurrentflow.(cuzmultimetermeasuresresistancebyinjectingcurrent.Won’tworkproperlyifthereisalreadycurrent!)○ Hmeanshold.Pressbutton.○ Batterymeanslowbattery.○ 1meansbigvalue,setupwrong.

○ 0meanschangemultimeter.○ SettingsarecorrectlysetforuinAlevels.Don’tchange.● Micrometerscrewgauge○ Don’tover-tightenit.Turnthimble→makecontactwithobject→turnratchet→3clicksenough.● Verniercaliper○ Thingstickingoutiscalled“depthprobe”. Calculationsandcommonerrorsbyyourstruly ● Uncertainty○ Absoluteuncertainty■ Precisionofinstrumentmultipliedby3-5duetoexpterror● Ifmax-minmethod/mathematicalmethodgivesbiggerabsuc,useitinstead.■ Thismultiplicationisnotshowneg ∆𝑡𝑡 = 3𝑤ℎ𝑎𝑡𝑒𝑣𝑒𝑟 𝑥 100%■ Rememberx100%■ 1sf■ Fortime:absoluteucjustwrite3■ Length:0.1cmx3=0.3cm■ Noneedx3formeasurementsofdiameter.Nohumanerror.○ Percentageuncertainty■ leftto2sf■ Writtenas__%,notasadecimal○ Chooseavalueof(variable)touseinfollowingexperiments■ Concepttested:uncertainty■ “Absoluteuncertaintyislarge.Toreducepercentageuncertainty,valueischosentogivelargestvalue” ● Calculatingconstants○ Followsfanddprules○ Otherthanlookingatsubstitutedvaluestofindthesmallestsf,seeiftheexpressionforconstantonlyhasgradient&y-intercept→smallestsfis3sf

○ Needunits○ Appliestoproportionalityconstant ● Calculategradient/y-intercept○ 3sf○ Nounits○ “CalculategradientGofthetangent”←questionwantsgradient,notaconstant.Gisaplaceholdertosignifygradient. ● Justifyyoursfgiventoconstant1. Constanthasthesamesignificantfiguresastheleastsignificantfigureofthevaluessubstituted2. (variab